Closed or open loop ?

[shmbry]

Can anyone tell me if this an open or closed loop system. Many thanks.

 

[Mobiltech]

Open loop. Variable displacement.

 

[funwithfuel]

Open loop. Variable displacement.

Where do you see variable displacement. I see fixed displacement

 

[funwithfuel]

.

 

[Mobiltech]

Sorry. I see your right. I saw the electric motor and thought it was controlling output.

 

[funwithfuel]

I see a single direction DC motor, shaft driving the fixed displacement motor. I see the DC motor depending on a demand of a function to energize the motor solenoid. In fact it looks very similar to a liftgate power pack running a small backhoe.

 

[funwithfuel]

Sorry. I see your right. I saw the electric motor and thought it was controlling output.

That's ok, I originally thought it was closed center because I failed to see the return running straight through off the main relief on first glance.

 

[CraneMechanic73]

a little rusty on the hydraulic 101 stuff. Your saying it’s open loop because of the return off the 160 bar relief?

 

[funwithfuel]

a little rusty on the hydraulic 101 stuff. Your saying it’s open loop because of the return off the 160 bar relief?

Yes, all the pump oil hits the pressure reducing valve but runs past it to the return channel. When a function is used, it closes the return passage and performs work up to the value set by the reducing valve, in this case 150 bar. Then the reducing valve opens dumping back to tank.

 

[terex herder]

The pump gets all its oil from the tank, and all oil is returned to the tank. Open system. A closed loop system will have oil being returned to the pump with a bleed off oil being returned to the tank via a filter, and a charge pump to make up for the lost oil.

Closed loop works great for constant volume systems, such as running motors, hydrostatic drive systems. Not so good for systems that change volume, such as cylinders. When both situations are needed, there is usually a open loop gear pump on the back of the closed loop piston pump.